Explain this to me...

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neumann

neumann

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First off, I mean no disrespect to any of the seasoned veterans of brewing on this board. I still hold the consensus of this board way over anything someone at my LHBS or just walking down the street has to tell me. My confusion (at least today's) comes from the whole airlock bubbling (or lack thereof) not being a sign of fermentation. Here is how I understand it: CO2 is a byproduct of fermentation and if you know you have an air tight seal on your fermenter (I understand that the buckets aren't usually airtight but Better Bottles and glass carboys ought to be) where is that CO2 going? I still get that the most accurate way to judge fermentation is via gravity readings. I'm just a little perplexed...
 
It is leaking out, because people make mistakes, or have a lack of attention to detail, or there is no liquid in the airlock :D

You CAN expect to see bubbles, but since there are factors that will allow pressure to escape by other means, the ONLY SURE way to tell if it is fermenting is with a gravity reading, because that is absolute.

This being said, in 5 years, mine have all bubbled.:drunk:

Bubbling airlocks are not direclty tied to fermentation, only a drop in SG is.

Airlocks will also bubble if there is no fermentation taking place... they will also go in REVERSE evn if there is fermentation taking place. SG is the only indicator.
 
My airlock never bubbles. Never, never ever. The CO2 is finding it's way out of my primary (I always use the same one) so I get no bubbles. My beer does just fine though.
 
It is an indication not hard evidence. At the end of the cycle the expelling of CO2 can be so minimal that you miss it when you look for airlock activity and consider it done when it is not. I like Revvy's point that it a pressure release valve and nothing else.
I think the deal is that so many people do not know that their vessel is airtight save for the airlock so they get themselves worked up when they don't see bubbles.
Often fermentation is not signalled as soon as I expect it but I can tell if the yeast is beginning to work simply by the changes in the top of the beer. Soon after the bubbling commences.
A butter knife is not a screwdriver.
 
To add to this, and I was rofl when I read the Revvy rant on airlocks and fermentation. I must say that I did also learn something so it was helpful.
For purposes of discussion, couldn't the amount of co2 being produced by the yeast actually not exerting enough pressure to create bubbles, just maintaining pressure? I likened this to my experience when using a blowoff tube in a glass carboy(I agree that it could be leaking from around the tube int he carboy.
 
neumann said:
But it will work in a pinch...
Click to expand...

The fact remains that fermentation is not complete until your Specific Gravity reaches it's terminal point. This being accomplished once all fermentable sugars have been consumed by your yeast. The argument here on these forums relative to airlock activity is not that it is not a sign of fermentation, it is that airlock activity should not be your primary indicator, particularly for determining completion of fermentation. Use the "right" tool for the job, a hydrometer.
 
ChshreCat said:
No such thing. My hydrometer samples end up in the same place as my finished beer. :D
Click to expand...
I lol'd. But seriously, can it be said that if the airlock is still bubbling, than fermentation can not be done, right? I know that just cause it's not bubbling doesn't mean it's not done but is there even any point to taking a hydrometer reading if the airlock is still bubbling?
 
It can also just bubble from degassing, like if you rack to a secondary sometimes the wort will expel CO2, even though its pretty much done fermenting. Or if the temp goes up, since less gas stays in solution in warmer liquids.
 
neumann said:
I lol'd. But seriously, can it be said that if the airlock is still bubbling, than fermentation can not be done, right? I know that just cause it's not bubbling doesn't mean it's not done but is there even any point to taking a hydrometer reading if the airlock is still bubbling?
Click to expand...

I dont know about that. I would say that is not entirely true. You could have some co2 coming out of solution. A few weeks back , I cold crashed my carboy to 32deg. It started bubbling once every 3 sec. Perhaps it was co2 coming out of solution or a change in pressure.
 
neumann said:
I lol'd. But seriously, can it be said that if the airlock is still bubbling, than fermentation can not be done, right?
Click to expand...

Incorrect. Fermentation can be complete and you can still have airlock activity due to the release of gasses. This can be particularly true in the case of beer that becomes fairly carbonated during fermentation. A personal example of this would be my recent Oktoberfest lager. It was a shock to me to find that there was quite a lot of carbonation in the primary vessel when I confirmed that fermentation was complete by using my hydrometer.
 
Once again this board impresses me with it's wealth of knowledge, willingness to dispense it, and complete lack of snottiness. To you-my fellow homebrewers
 
I'm one of the few (I guess) that does go by the airlock (and other visible signs, I use a glass carboy so it's easy to see the beer). But I am aware of the offgassing, leaks, etc. that could be misleading. I don't take a hydro reading until I'm racking it (in which case I'm really 'catching' a sample which is a little more sanitary) basically because I'm 99.9% sure it's done. IMO, it doesn't really take that much experience to be able to tell by monitoring the fermentation when it's done. In many/most cases, we're not racking the beer until weeks after it's actually done with the main fermentation so it's often a non-issue anyway.

Also, I rack my lagers after only 8-10 days and let them naturally carbonate in the keg. I don't measure the gravity here either (I do catch a sample while racking though)...I just rack it the corny when I think it's time and it's always right about where I think it is (about 3-4 points shy of terminal gravity).

I agree that inexperienced brewers shouldn't rely on this but I think with just little experience it's OK.

So IMO, you don't need a hydrometer sample to know when it's done fermenting just like you don't need a meat thermometer to know when your steak is medium-rare. But I do need to know the FG so I always 'catch' a hydro sample.
 
olllllo said:
Not all off-gassing is a result of fermentation.
You can get off-gassing from temperature change alone.
Click to expand...

And, believe it or not, changes in barometric pressure can cause airlock activity in a completed fermentation. I've had suck-back, as well as bubbling, only due to a storm front moving in!

I think as you gain more experience, as SpanishCastleAle said, you can actually guestimate where you are in the fermentation better than you could without the experience. While I don't rely on airlock activity, I often can gauge about where I am. I confirm with a hydrometer, though. I can also use visual clues. As an example, I have a 7 day old AAA. It's been bubbling pretty slowly at 64 degrees. But I thought I'd check on it, and see if I could rack it. I pulled out the sample, and wow- is it cloudy! Full of suspended yeast and bubbly with co2. So, I knew that it wasn't at FG even before putting my hydrometer in. And, it was at 1.026, like I suspected. So, visual clues (dropping of krausen, cloudy wort), airlock activity, etc, all can be used by an experienced brewer without pulling out a hydrometer each time.

If the beer is crystal clear, without airlock activity, and it's been a couple of weeks, you can probably guess with reasonable certainty that it's done. But, confirm it with a hydrometer before bottling!

The other thing to keep in mind is something that is unique to those of us who keg. We can keg the beer, even if we're not at FG, if we like the beer where it is. We have no danger of bottle bombs, so we can be more relaxed. Of course if the beer is sweet and underattenuated, we'll let it sit longer. But if it's a couple gravity points higher than I'd like if I was bottling, I just shrug. It's easier to be relaxed when you're not concerned about underattenuation or bottle bombs!
 
YooperBrew said:
And, believe it or not, changes in barometric pressure can cause airlock activity in a completed fermentation. I've had suck-back, as well as bubbling, only due to a storm front moving in!

I think as you gain more experience, as SpanishCastleAle said, you can actually guestimate where you are in the fermentation better than you could without the experience. While I don't rely on airlock activity, I often can gauge about where I am. I confirm with a hydrometer, though. I can also use visual clues. As an example, I have a 7 day old AAA. It's been bubbling pretty slowly at 64 degrees. But I thought I'd check on it, and see if I could rack it. I pulled out the sample, and wow- is it cloudy! Full of suspended yeast and bubbly with co2. So, I knew that it wasn't at FG even before putting my hydrometer in. And, it was at 1.026, like I suspected. So, visual clues (dropping of krausen, cloudy wort), airlock activity, etc, all can be used by an experienced brewer without pulling out a hydrometer each time.

If the beer is crystal clear, without airlock activity, and it's been a couple of weeks, you can probably guess with reasonable certainty that it's done. But, confirm it with a hydrometer before bottling!

The other thing to keep in mind is something that is unique to those of us who keg. We can keg the beer, even if we're not at FG, if we like the beer where it is. We have no danger of bottle bombs, so we can be more relaxed. Of course if the beer is sweet and underattenuated, we'll let it sit longer. But if it's a couple gravity points higher than I'd like if I was bottling, I just shrug. It's easier to be relaxed when you're not concerned about underattenuation or bottle bombs!
Click to expand...

+1. Pretty much everything I had in mind to add to this thread.

I only use buckets for primary, because they are easy to clean, easy to move, large enough to hold all that wort, etc, etc. Usually I can see airlock activity, but this last time, because I used a different or for whatever reason, no airlock activity. Experience tells me though, that if I lift the lid and see krausen, and sniff that wonderful aroma of CO2, then it's working.

The Hydrometer verifies what I suspect.
 
You can have bubbles with no fermentation:
  • Wort temperature rises when no fermentation is taking place = bubbles from increase in internal pressure due to expansion
  • Barometric falls when no fermentation is taking place = bubbles due to pressure gradient from inside to outside
  • Beer (fermented wort), temperature rises after all fermentation is complete - CO2 leaves solution = bubbles
  • You just dryhopped, and the nucleation points in the hop fragments cause CO2 to leave solution in spite of the cessation of fermentation = bubbles

You can have fermentation with no bubbles:
  • Fermentation is happening, but there's a leak = no bubbles
  • Fermentation is happening, but temperature is falling = no bubbles - wort is shrinking in volume, opening up headspace
  • Fermentation is happening, but barometric pressure is rising = no bubbles due to adverse pressure gradient
  • Fermentation has begun, but wort is absorbing CO2 into solution = no bubbles due to absorption
  • Fermentation is happening, but temperature is falling, CO2 entering solution = no bubbles due to absorption

For these reasons, and many others, we don't rely on the bubbles to tell us anything more than "it's bubbling". People, especially new brewers, freak out because of the existence or lack therof of bubbles, and that's why the "pay no attention to the bubbles" mantra is oft repeated.
 
Actually, there are several reasons for no bubbling in the airlock. In my case, I use a 5 gallon bucket to ferment 2.5 gallons, not sure what you use, so I have a lot of headspace between the top of the bucket and the top of the brew. When fermenting your beer is producing CO2 as a byproduct, TRUE, but it really isn't producing a lot. Have you ever poured your ferement into a glass? Try it next time you brew. You will notice no "carbonation" hence there just isn't enough being produced. You mentioned a carboy. Depending on which airlock and what your setup is like, it is possible that you put a little too much water in the air lock and the CO2 cannot overcome the density of the water. So in essence you are trapping the the CO2. Most of the time this causes blowoff though and since you did not ask about a bottle blowing up I will assume you aren't having those issues. If I were you, I would thief a little bit out and taste it. It should taste like flat beer.

PS Im a cheapy and never purchased a hydrometer. Taste is the earliest known measuring tool to brewing gods.

**edit - forgot to mention. CO2 is denser than air. Often times if you have just the right amount of air, the air creates a blanket over the lid and the carbonation forces the air upwards and cannot escape. Air isn't dense enough to move through the airlock and bubble, so no bubbly airlock.
 
bigin31 said:
**edit - forgot to mention. CO2 is denser than air. Often times if you have just the right amount of air, the air creates a blanket over the lid and the carbonation forces the air upwards and cannot escape. Air isn't dense enough to move through the airlock and bubble, so no bubbly airlock.
Click to expand...

This is kind of really wrong....Air will bubble just as much as CO2, (blow into your straw...bubbles!)....but the rest of what you said is copacetic.
 
Your forgetting one thing. When you blow into a straw you are applying force pounds to the air in the straw. When you use an airlock you depend on atmospheric pressure, which is much less than the amount of force you can blow into a straw.
 

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